A 66-year-old hypertensive smoker reports dizziness and visual blurring that occur reproducibly when he uses his right arm for overhead work. Right radial pulse is weaker than left, right arm systolic pressure is 35 mmHg lower than left, and a bruit is audible above the right clavicle. What is the diagnosis?

• A Subclavian steal syndrome ✓
• B Vertebrobasilar insufficiency from intracranial atherosclerosis
• C Neurogenic thoracic outlet syndrome
• D Carotid artery dissection

Explanation

Proximal subclavian artery stenosis lowers pressure distal to the lesion, so arm exercise diverts blood retrogradely down the ipsilateral vertebral artery to supply the arm, stealing flow from the vertebrobasilar circulation and causing posterior circulation symptoms. An interarm systolic pressure difference greater than 20 mmHg with a supraclavicular bruit supports this. Thoracic outlet compresses nerve or vein rather than producing vertebrobasilar symptoms, and carotid dissection causes neck pain with Horner syndrome or cerebral ischaemia.

Reference: Bailey and Love's Short Practice of Surgery, 27th ed.

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Written and medically reviewed by the StethoPrep medical team.